It has been proposed to use resistive storage elements in memory cells to provide non-volatile data storage. Such elements are programmable to adopt one of two different resistive states. The programmed resistive state is maintained even when a supply voltage of the memory cell is disconnected, and thus data can be stored by such elements in a non-volatile fashion.
Various types of programmable resistive storage elements have been proposed, some of which are magnetic storage elements capable of being programmed by the direction of a current that is passed through the element. An example of such a current-programmable magnetic storage element is a magnetic tunnel junction having a write mechanism based on spin transfer torque (STT) or spin orbit torque (SOT).
Other examples of programmable resistive storage elements include those used to form PCRAM (Phase Change Random Access Memory), OxRAM (metal Oxide RAM) and CBRAM (Conductive Bridging RAM).
In a memory array comprising programmable storage elements, each memory cell generally comprises several transistors that permit the memory cell to be selected and programmed. It would however be desirable to reduce the surface area of each memory cell in order to provide a non-volatile memory having greater density, and thus more storage capacity and/or a reduced overall surface area.